adding release workflow (#12)

Author: dfm

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"

.github/workflows/tests.yml

@@ -48,3 +48,37 @@ jobs:
         run: |
           python -m nox --non-interactive --error-on-missing-interpreter \
             --session "${{matrix.session}}-${{matrix.python-version}}"
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-python@v4
+        name: Install Python
+        with:
+          python-version: "3.9"
+      - name: Build sdist and wheel
+        run: |
+          python -m pip install -U pip
+          python -m pip install -U build
+          python -m build .
+      - uses: actions/upload-artifact@v3
+        with:
+          path: dist/*
+
+  upload_pypi:
+    needs: [tests, build]
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/')
+    steps:
+      - uses: actions/download-artifact@v3
+        with:
+          name: artifact
+          path: dist
+
+      - uses: pypa/gh-action-pypi-publish@v1.6.4
+        with:
+          user: __token__
+          password: ${{ secrets.pypi_password }}